The invention relates to fuel injection systems for internal combustion engines.
Fuel injection systems for internal combustion engines are generally of two types. One type is a high pressure system wherein pressurized fuel is supplied to a high pressure precision fuel injector which emits fuel for combustion in the engine. A high pressure fuel injector is a costly, precision part and must be actuated between on (passing) and off (blocking) states. The other type of fuel injection system is a low pressure system wherein fuel continuously flows through a low pressure fuel injector. A low pressure fuel injector is simple and inexpensive and is not actuated between on and off states, but rather is on all the time and continuously passes fuel therethrough. The present invention relates to the latter type fuel injection system.
The present invention provides improvements in continuous flow fuel injection systems, including reduced fuel heating, reduced wear, longer service life, simplification, and reduced number of parts. An electric fuel pump is energized with a variable duty cycle to vary the pumped volume output of the pump according to engine fuel requirements. This is particularly advantageous in applications where the engine is operated at idle or low speeds for extended durations because the pump is not continuously running and heating the fuel. The duty cycle is varied to energize the pump to pump substantially only the amount of fuel required by the engine, such that at low engine speed, the pump is energized a lower percentage of the time than at high engine speed. This reduces pump wear. Fuel flow through the fuel injector is continuous but energization of the pump is not. The pump is not pumping at full capacity when unneeded. This increases service life. Part content is reduced by eliminating the need for a solenoid or other metering device at the fuel injector inlet.